In one conventional belt manufacture, the body of rubber is looped and provided on its inner surface with a cover fabric. In one form of such belt, the inner surface is undulated so as to define a series of cogs.
It is also known to provide such cogs in the outer surface of the belt, which outer surface may similarly be provided with a cover layer of fabric.
It has been conventional in forming such belts to firstly form a preform consisting of one or more layers of fabric and an overlying body of compression rubber. An overlying layer of cushion rubber for accepting the tensile cords of the belt may be provided on the upper surface of the preform. The preform is wrapped about a cylindrical grooved mandrel adapted to receive the cogged portions of the preform. Opposite ends of the preform are juxtaposed. The tensile cords may then be wrapped around the preform on the mandrel, an outer cushion rubber layer placed around the tensile cords, and an outer layer of tensile rubber wrapped thereabout. If desired, an outer layer of fabric may also be wrapped around the outer layer of tensile rubber. This assembly is then cured by suitable heating so as to vulcanize the rubber to form a belt sleeve which is then slit circumferentially to define a plurality of individual V-belts.
Where the outer tensile rubber portion of the belt is cogged, a preform similar to that provided for forming the compression portion of the belt may be formed and wrapped about the outer cushion rubber layer. An outer grooved mold may be engaged with the outwardly facing cogged layer in forming the inner and outer cogged belt sleeve.
A problem arises in such manufacture in that it has been conventional to cut the preform so as to define juxtaposed end surfaces when wrapped about the mandrel. As the joint thus produced extends fully through the tensile rubber and fabric, a problem has arisen in the failure of such joint in use, notwithstanding the attempted bonding of the opposite ends of the preform during the belt molding operation on the mandrel.